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Re: vibration vs. oscillation



Todd Pedlar wrote:

A quibble on this statement, Carl. Rotational energy is definitely not
internal.

Haskell and Denker have already written clear reasons to take
exception with this quibble. I'd like to give you one more situation
to chew on:

Suppose a ball rolls without slipping down a rough inclined plane. I
am guessing you would like to call this an example of conservation of
mechanical energy: gravitational PE is converted into bulk
translational and rotational energy since static friction does no
work. This argument can be found in many intro books, but IMHO it's
nonsense.

By the same logic, if I start from rest and accelerate up to walking
speed without slipping on a level floor, my mechanical energy has
been conserved!!

Obviously something is rotten in the state of Denmark. I'll resist
the temptation to say more now, but I have a review article coming up
in the September issue of The Physics Teacher which deals with such
issues. Carl
--
Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5040
mailto:mungan@usna.edu http://usna.edu/Users/physics/mungan/